CAMBRIDGE — Secretary of State John Kerry, who rose to national prominence as a Vietnam War veteran speaking out against the conflict after he returned home, said Tuesday that the United States is working to challenge the Islamic State in a fashion that does not lead to an on-the-ground American military presence in a bigger conflagration.

“We’re trying to do that in a way that doesn’t embroil us in a larger war and once again go through a routine of young Americans being on the ground in a Middle Eastern or other country in the region with a predominant Muslim population and fighting yet again,” Kerry said, speaking to Harvard professor Graham Allison at an event at the Charles Hotel.

Kerry indicated the United States has been very careful in its efforts and tried to boost local opposition to the Islamic State.

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That has not panned out as well as people had thought it might, so “we are rethinking, and retooling a bunch of different options,” he said, appearing to allude to the recent US decision to quit its attempt to train thousands of fighters in Syria to combat the militant group, also known as ISIS or ISIL.

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But regardless of US strategy, the secretary said the Islamic State ultimately “has no long-term future.”

Kerry, answering questions from Allison, director of Harvard’s Belfer Center for Science and International Affairs, and Harvard students, spoke at length, and sometimes discursively, about international figures and issues from President Vladimir Putin of Russia to conflict in South Sudan to fighting AIDS across the world.

But the nation’s top diplomat wasn’t always diplomatic.

Kerry, a 1966 graduate of Yale University, said he had represented Harvard as one of Massachusetts’ senators for 28 years.

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“I will not remind you it takes a Yale man to do that properly,” he said to laughter before remarking: “I’m really getting on thin ice fast.”

Still, Allison and the crowd were largely friendly and the secretary’s remarks were interrupted by applause.

The event came after two days of Kerry employing his Beantown brand of hometown diplomacy. On Monday and Tuesday, Kerry huddled with top Australian officials and Secretary of Defense Ashton Carter at locations such as the Boston Public Library.

Speaking to reporters Tuesday afternoon, Kerry, Carter, and their Australian counterparts said they spoke about issues ranging from combating terrorism to tensions in the South China Sea.

At the press conference, Kerry condemned the recent uptick in violence in Israel and the Palestinian territories, but declined to directly apportion blame.

“It is absolutely critical to see the violence and incitement stop wherever it may be,” he said. “And I’m not going to point fingers from afar, but when I have knowledge of violence that has taken place that shouldn’t have, like the stabbing of three innocent Israelis by nothing more than terrorists, we will condemn it.”

“The families themselves of these hostages knew exactly what our strategy was and why it was important not to hold a nuclear agreement hostage to hostages. And in our judgment, it was the right thing to do because it could have complicated both significantly and perhaps have resulted in nothing happening on either,” Kerry said. “So I think we did — it was the right strategy to pursue.”

Kerry also emphasized the United States is continuing discussions with the Iranians about American citizens, and will do so until they come home.

Amid all the serious talk, Bishop, the foreign minister, went out of her way to praise Kerry’s hospitality and said she had been keen to return to Boston after spending some time at Harvard Business School in 1996.

“I fell in love with this elegant city at that time, with its history of intellectual thought, of fierce and robust debate, and I hope we had some of that during the course of our dialogue today,” she said at the press conference at the Revere Hotel in Boston.

Tuesday’s Hub diplomacy isn’t the first time Kerry, a former senator and Democratic nominee for president who became the nation’s top diplomat in February 2013, has used Massachusetts as a venue for connecting with world leaders. He has dined in the state with Prime Minister Shinzo Abe of Japan on a meal prepared by Boston restaurateur Barbara Lynch, and admired the wares at Quincy Market with Foreign Secretary Philip Hammond of Great Britain.